Polyurethane rubbers have broad utility in the fashioning of flexible, strong articles. However, conventional polyurethane elastomers are found to be relatively incompatible with extender oils due to the nature of their polyether or polyester soft segment. Polar oils might be used with these commercial polyurethanes but they soften the rigid urethane hard segments to an unacceptable extent. Therefore, polyether-and polyester-based polyurethane rubbers, while flexible and strong, are relatively hard and are not easily compounded with extender oils.